What is the stretch-out measurement for the throat of a 12" x 8" rectangular duct elbow at 60 degrees, with a throat radius of 9"?

To determine the stretch-out measurement for the throat of a rectangular duct elbow, you must consider the dimensions of the duct itself and the geometric relationships involved in the elbow design. The stretch-out measurement is the total length of sheet metal required to create the elbow.

In this specific case of a 12" x 8" duct elbow at 60 degrees with a throat radius of 9", you can derive the stretch-out by analyzing the geometry. The calculation for the stretch-out at the throat generally considers the length of the duct's sides and the impact of the angle.

For a rectangular elbow, the stretch-out is calculated by taking the longer dimension (12") and adding the arcs generated by the elbow's radius. Given that the throat radius is 9", the arcs created by the rounded corners of the elbow will add some additional length to the straight sections of the duct.

The specific math can be worked out by understanding that the angle of 60 degrees effectively creates a sector form in the layout that must be compensated for in the final stretch-out. This geometric approach to calculating the stretch-out yields a measurement of 9 7/16".

This result aligns with the principles of sheet metal fabrications, where accurate accounting for angles and radii is